1. Field of the Invention
Aspects of the present invention relate to methods of preparing a reduced graphene oxide (RGO) and an RGO-polymer composites, and more particularly, to methods of preparing an RGO and an RGO-polymer composites that have high electrical conductivities from graphene oxide.
2. Description of the Related Art
Graphite oxides or graphene oxides oxidized from graphite have high dispersibility with respect to a hydrophilic solvent, but they have low electrical conductivity (3.7×10−7 S/cm), and thus, they are not suitable for use in applications requiring high electrical conductivity. Thus, to address this problem, the reduction of graphene oxide is needed. As a method of reducing graphene oxide, a chemical reduction method and a thermal reduction method are known.
The chemical reduction method is performed using various reducing agents, such as NaBH4, HI/AcOH, NaOH/KOH/NH3, metal, phenylhydrazine, and the like, and graphene with tens to hundreds S/cm of electrical conductivity can be mass-synthesized by using the chemical reduction method. In the case of reduced graphenes, however, they tend to agglomerate to each other by the Van der Waals' Force and thus it is difficult to uniformly disperse the graphenes in a solvent (<1 mg/mL). Therefore, to prepare graphene-polymer composites in which graphene is uniformly dispersed in a solvent, graphene needs to be redispersed in a solvent.
In the thermal reduction method, graphene oxide is generally heat treated at high temperatures (1,000° C. or more), and graphene having an electrical conductivity of 55,000 to 100,000 S/m is obtained. However, the thermal reduction method is performed at high temperatures and thus energy loss problems may occur.